^ Success (sort of)!
Your photo shows the turn indicators illuminated in the rear bumper, not the rear-fog LEDs. My i3 does the same with the rear-fog switch activated, so I'm guessing we used similar codes.
Here's a BMW diagram of the left rear lights in an i3 exterior, along with their functions. The turn indicator is 5, while the rear fog is 7.
What we have is OK, but I would like to figure out how to activate just the rear fog (7) with the switch, as BMW intended. While 5 is bright, those LEDs appear to be part of a dynamic braking system, which activates additional rear lights with hard stops. I'm curious to what extent setting 5 as rear fogs affect activation of additional lighting under hard braking. Eventually, I’ll test the current set up with hard braking and report results. Again, there's probably a compelling reason why BMW created a discrete rear-fog LED (7) in the i3.
And for North American i3 drivers, see this well-illustrated, how-to guide for making the blank button active in a headlight switch similar to the i3's. If your X-acto knife and BimmerCode skills are robust, this seems like an inexpensive way to activate the rear-fog (minus the illuminated symbol).
https://www.normalexception.net/BMW-F36 ... -foglight/